1. Field of the Invention
The present invention relates to an array substrate having an auxiliary capacitance line and a correction method of the array substrate.
2. Description of the Related Art
In recent years, liquid crystal display devices are widely used as display units of household electrical appliances such as computers and televisions. A liquid crystal display device generally comprises an array substrate and a color filter substrate, which are facing to each other with a narrow gap therebetween and bonded together at their peripheral portions, and a liquid crystal filled in the gap. On the array substrate, scanning lines and signal lines are arranged perpendicular to each other in a reticular pattern. In each of pixel regions partitioned by the scanning lines and the signal lines, a pixel electrode is arranged. The pixel electrode and the signal line are connected via a switching element which is on/off controlled by the scanning line. In addition, on the array substrate, an auxiliary capacitance line is arranged overlapping the pixel electrode so that the electric charge which is supplied from the scanning line and stored in the pixel electrode is maintained longer.
Although the electric charge stored in the pixel electrode gradually leaks via the liquid crystal layer and the switching element and therefore decreases by the next application of signal voltage through the scanning line, the decrease is suppressed by the auxiliary capacitance line arranged overlapping the pixel electrode. In general, when the overlapping area of the pixel electrode and the auxiliary capacitance line is larger, the ability to maintain the electric charge stored in the pixel electrode is greater. However, a larger overlapping area results in a lower aperture ratio of the pixel electrode.
This type of liquid crystal display device is disclosed in Japanese Patent Application Unexamined Publication No. 2004-53752. As shown in FIG. 6, an auxiliary capacitance line 51 of an array substrate 50 of this type of liquid crystal display device has a line trunk 51a arranged parallel to a scanning line 52 and line branches 51b extending from the line trunk 51a. The line branches 51b are used to increase the ability to maintain the electric charge stored in a pixel electrode 53. The line branches 51b are arranged along signal lines 54 which are shielded from light by black matrixes of a color filter substrate, thereby suppressing decrease in the aperture ratio.
However, providing the auxiliary capacitance line 51 with the line branches 51b results in interposing a foreign matter such as a conductive foreign matter and causing a short circuit between the pixel electrode 53 and the auxiliary capacitance line 51. Accordingly, the possibility of point defect is increased. When a point defect occurs, the short circuit can be corrected by applying a laser beam to the short-circuited line branch 51b in order to cut it at some midpoint. However, if the insulating layer between the pixel electrode 53 and the auxiliary capacitance line 51 is thin, the laser beam is also applied to the pixel electrode 53.
Although there is another correction method in which the short-circuited area is isolated from the other area of the pixel electrode 53 by applying a laser beam to the pixel electrode 53, this method is difficult to perform because it is difficult to completely isolate and insulate the short-circuited area from the other area of the pixel electrode 53 and thus some area tends to remain connected.
Hence, the present invention aims to provide an array substrate, a correction method of the array substrate, and a liquid crystal display device which can easily correct the above defect.